$(function() {
	airBalloon('div.air-balloon');
});

/*
 * @function 热气球移动 @update by julying , 2012/7/25
 */
function airBalloon(balloon) {
	var viewSize = [], viewWidth = 0, viewHeight = 0;
	resize();
	$(balloon).each(function() {
		$(this).css({
			top : rand(40, viewHeight * 0.5),
			left : rand(10, viewWidth - $(this).width())
		});
		fly(this);
	});
	$(window).resize(function() {
		resize()
		$(balloon).each(function() {
			$(this).stop().animate({
				top : rand(40, viewHeight * 0.5),
				left : rand(10, viewWidth - $(this).width())
			}, 1000, function() {
				fly(this);
			});
		});
	});
	function resize() {
		viewSize = getViewSize();
		viewWidth = $(document).width();
		viewHeight = viewSize[1];
	}
	function fly(obj) {
		var $obj = $(obj);
		var currentTop = parseInt($obj.css('top'));
		var currentLeft = parseInt($obj.css('left'));
		var targetLeft = rand(10, viewWidth - $obj.width());
		var targetTop = rand(40, viewHeight / 2);
		/* 求两点之间的距离 */
		var removing = Math.sqrt(Math.pow(targetLeft - currentLeft, 2)
				+ Math.pow(targetTop - currentTop, 2));
		/* 每秒移动24px ，计算所需要的时间，从而保持 气球的速度恒定 */
		var moveTime = removing / 24;
		$obj.animate({
			top : targetTop,
			left : targetLeft
		}, moveTime * 1000, function() {
			setTimeout(function() {
				fly(obj);
			}, rand(1000, 3000));
		});
	}
};